Some mist sprayers can be observed to have back suction during the actuator is released after each pressing. It means the residual liquid on the nozzle will go back into the nozzle hole. However, for non-ball structure pumps, no such back suction is ovserved. See the attached vedio for details.
The reason of back suction is that for a ball structure pump, a short time at the beginning of releasing the actuator exists. During that time, the valve connecting the channels of stem/piston and inner pump/housing is opened. Even though this valve closes quickly, sometimes a little liquid will still go back into the inner pump/housing. However, for the non-ball structure, such valve closes immediately after the dose is sprayed out. Therefore, when release the actuator, the valve already closes, so no liquid will go back into the inner pump/housing.
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